Carb talk...

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§mokiee

Member
i'm thinking about buying a 66 riviera with a 425 nailhead on it...buy i saw other 425's with 2 or even 3 carbs on them wat the difference if i get 1 or 2 or3 carbs on the car?

p.s. how much HP is on a 425 nailhead on a 66 riviera/
 
The car should have a Quadrajet carb on it. Good carb. Multiple carbs are mostly for looks and are more difficult to tune.
 
If you have an ol school mechanic tune your dual carbs youll be doing 100mph before even opening up all the way. You can stroke a 425 to 454cid and get close to 420ish plus horse power.
 
Correct that. The nailheads had carter afb's on the dual carb setup. All the idle adjustments were done on the front while the rear hd no choke. Have a set sitting in dads garage.
 
Troy the REAR carb is the one with the idle and mixture screws on it and it is what the motor runs on until the front primaries are needed and then the secondaries will open in tandem when the throttle has moved further and then you end up with all 8 barrels working to feed that 425( which can be stroked to a 464).
I have a bare 2 x 4 manifold so maybe one of us could sell the other the carbs/intake?
Don't get me wrong as I would love a set of dual quads on a nail IF the EELCO aluminum intake EVER gets tested and shows that it is at least as good as the old Edelbrock dual quad. Gessler gets $425. to modify the stock intake and that is what the EELCO sells for. There is not much to tune as you tune the REAR carb just like it were the only carb on the motor and get the linkage set correctly but it is still more for looks with a single carb making as much power and for less ca$h than the duals. I have had the duals and a Thermoquad on a 401 and the T-Quad worked great and they are still available and for a good price!
 
A full boogie set of heads don't flow enough to support the cubes of a good running 322, how they going to support 464?????

Tom T.
 
You can stroke and bore a later 425 because the cylinder wall will take the cut. You have to modify the crank, pistons, rods, combustion chamber and so on to get up to 454 displacement. If you can go bigger great, but I only personally know of 454 cid stroked. My dads original afb dual quad setup is not for sale. It came off a car and engine he has as a kid. Like I said, he was in the 100mph before opening up the rear. Grampa and dad both were Buick mechs.
 
'nailheads'

The Buick 'nailhead' is an interesting engine. It has some very desirable features, but then it stops and ends with some very strange quirks. It has a pentroof combustion chamber, which is what many modern engines have today. [see honda] and it has excellent intake porting, very direct and unhindered.But then when you get to the exhaust ports, They couldnt be worse! Its as thought they tried to make it bad!A worse port would be hard to find! its very obvious that 'GENERAL CORP' said 'WHOA'. They were onto an engine design that would have knocked the socks off of every engine made at the time.especially at GM. the Kettering Cadillac engine was at the top of engine designs, of the day. But the BUICK V8 had the beginnings of a world class motor. They stopped at the exhaust layout and made a TRUCK engine outta it.
just stop! and look at a drawing of the head ports.Imagine another rocker arm setup onthe exhaust side, what do you see? A whole new set of rocker arms and valves! With the same porting and valves as the intake, and you have a 'PENTROOF 4 VALVE HEAD'. 4 VALVES PER CYLINDER! Look up 'pentroof' on the web to see. I am sure the buick engineers knew about this and were directed not to use that technology.I think of that everytime i look at a 'NAILHEAD'!
 
Cool cutaways!!!! I read your first post and had to scratch my head. Then when I saw the pics... Ahhhhhh! You're right. I think the gm techs might have been slapped by the men in black.
 
nailhead

And if you go a few steps further, dump the pushrods and think 'OVERHEAD CAMS. it would be pure 'EXOTIC'. I bet they actually made one! Has anyone everheard of that?

Just thinkin out loud:clonk:
 
I did hear of a local dirt track racer who moved the exhaust valve to the other side of the chamber to make it like a true HEMI and flow much better but that is all Im know.
 
After many hours on a flow bench, designing "Adjustable Roller Tip Rocker Arms", all for the ole "Nail", although the exhaust does have it's limitations, in a normally aspirated situation, it's NOT the exhaust that's the restriction & for many years the popular belief's, but the INTAKE!!!!!!!! Get the AIR in & it has no choice but to go out. Max got the "Nail" to run good & that's where he concentrated his most efforts in the design of his aluminum heads. Buick never did any experimental work with overhead cams, but they did get involved with aluminum heads, big port/d-port heads & turbo's. 39Cent is correct with the "Pent Roof" combustion chamber. Many of today's higher performance engine have this. So what's old is once "New" again. It's because it's a very efficient design that can run higher compression with today's "Quality" fuel without the drawbacks. Contrary to popular belief's it is a "Hemi" in it's own rights.

Tom T.
 
Tom, it seems a stock motor with it's approximate 9.9:1 compression can run at 30* total on 93 octane but it would seem that would be it without a larger cam that had more overlap unless you know something else you would care to share. Mark
 
nailheads

The thing that got me thinkin, was having them 2 little valves along the top for exhaust an intake! Then noticed the similarities of valve
arrangement on 4 valve heads! Gads all they needed was a little more pushrod monkey motion, 2 more ports, n, valves, and it would be a hemi killer!
 
I don't quite understand what your saying or asking Mark???? Most stocker type "Nails" can run 32* all in@, as low as, 22-2400RPM's. More initial advance gives better throttle response & gets a heavy car moving quicker. The trick is 36* as above but after 3800RPM's get the distributor to back off 4* to 32. Because of breathing capabilities & lack of valve lift AT THE VALVE most all "Nails" die at 5800RPM's. I don't care if you are using hydraulics, solids or a roller at 5800 it's over. Buick tried to make up with this with a very aggressive ramp rise profile on the cams they designed. Most engines with a .842" diameter lifter have about .003" rise per degree of camshaft rotation. Most rollers have about .008" rise. Many of the later "Nails", 401/425's had .007". This is a very aggressive ramp rise, the reason you could get away with running solids on your stock "Nail" hydraulic cam & have a performance boost. I could go on for days, but typing with one finger it would take weeks.

Tom T.
 
Tom since this thread seems to be going everywhich way I got even more offtrack than most, sorry. I understand and have seen that 30* total timing on '93 octane is the max and not bad considering those are about stock specs. I have also read that the HEMI placement of the sparkplug makes for a short, quick flame travel so I guess my question here is why can't more compression be ran? I am talking a true 11:1 static compression ratio.
Then looking at the drawings both the intake and exhaust have at least 90* turns to take. The intake looks like a straight shot but not with the valve angles like it is!
Also there seems to be few guys with a completed motor with complete mod/spec info available. I realize this is an old design motor but it does have a good cult following. Speaking of which in conversation with EELCO on friday they really don't have plans for a single aluminum 4bbl intake as they say there is little interest!!!!
I for one would rather run an 850cfm Thermoquad over anything else except or a nicely reworked Q-jet/800cfm.
Again read headers for the '66/'65 GS cars do not fit well, is this true and who makes the headers for TA/Poston? Well I have more questions but will limit it for now. If anyone has opinions or suggestions please ask/add!
 
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